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Classical Swine Fever E2 Subunit Marker Vaccine : Field Trial and Assessment of Protective Efficacy
|關鍵字:||Classical swine fever;豬瘟;E2 subunit vaccine;Protective Efficacy;E2次單位疫苗;保護效力||出版社:||獸醫病理學研究所||摘要:||
豬瘟E2次單位疫苗為近年來新開發出之標識疫苗，對豬瘟具有良好的保護效益。為進一步評估此次單位疫苗在本土試驗上對豬之保護及在田間使用上對本病防治之效益，以作為我國豬瘟清除計劃推行之參考。因此，本試驗以E2次單位疫苗仍針對一豬瘟污染場，以大規模免疫方式對全場母豬與6週齡以上豬隻進行免疫注射，爾後定期於4及8週齡時各免疫一次，田間試驗期間並針對部分試驗豬進行不同免疫計劃注射，包括4週齡豬隻經單次免疫或在2及6週齡各免疫一次等，定期採血，以ELISA (CeditestO CSF E2 Ab ELISA)及中和試驗檢測抗體之激發與持續狀況。由血清抗體結果顯示在2及6週齡和4及8週免疫的豬隻，其抗體均可維持到上市(PI=103.53-104.86%，SN=7.57-8.1 log2 )，而僅在4週齡免疫一次的豬隻，其抗體亦可維持到上市(PI=88.44±15.58%，SN=6.22±1.2 log2)，惟其平均抗體力價及整齊度略低於免疫兩次者。為進一步瞭解移行抗體之干擾現象，部分試驗豬之免疫計劃提前於2週齡免疫。此結果顯示移行抗體對E2次單位疫苗不具干擾現象，即使祇於2週齡免疫一次者，陽性ELIA抗體仍可維持至上市(PI=97.97%±10.54)或中和抗體力價可維持在128倍(7.25±1.13 log2)。為監控E2次單位疫苗於田間豬瘟污染場使用後，對於豬瘟清淨之效益，此監控結合病理、抗原ELISA及間接螢光染色法和RT-PCR等方法來監控豬場病弱族群之病毒潛在狀況，亦利用區別診斷試劑檢測Erns抗體呈現情形，以評估豬場之清淨度。在未進行免疫前，此污染場Erns抗原檢出率約為1.07%、Erns抗體檢出率約為20%。經E2次單位疫苗免疫後，健康肉豬群與病弱豬群均未曾有再遭受豬瘟病毒感染之證據。為進一步瞭解E2次單位疫苗在本土實驗之保護效力，因而，進行免疫後人工感染或同居感染之動物試驗，結果顯示E2次單位疫苗在免疫後2週即可產生足夠的中和抗體來抵抗豬瘟病毒的攻擊，豬隻均存活，但仍有些許的豬隻會有輕微發病但不會死亡，而在免疫後3週與補強後2週攻毒組均即可完全抵抗豬瘟病毒的攻擊及阻斷水平之傳染。綜合以上試驗結果顯示，E2次單位疫苗不僅不受移行抗體干擾，其抗體可在免疫後呈快速且穩定揚升並可持續至上市，這些中和抗體來抵抗豬瘟病毒株的攻擊，並可有效阻止豬瘟病毒的傳播；此外可利用區別診斷試劑以鑑別野外病毒之感染，此有助於我國對豬瘟清除之推行。
Classical swine fever (CSF) E2 subunit marker vaccine is new developed vaccine and can stimulate pigs developing good immune response against CSF virus infection. This study was aimed to evaluate the protective efficacy and control CSF virus infection in a virus contaminated pig farm using E2 subunit marker vaccine in Taiwan. Therefore, a massive vaccination program including all sows and pigs aged over 6-week-old were all vaccinated with E2 subunit marker vaccine in a CSF virus contaminated pig farm. Thereafter, piglets were regularly vaccinated with E2 subunit marker vaccine at 4- and 8-week-old. To evaluate the immune response of pigs stimulated with E2 subunit marker vaccine, several different vaccination programs including pigs receiving single vaccination at 4-week-old or double vaccinations at 2- and 6-week-old in some ear-tagged pigs were evaluated. CSF antibody were assayed by ELISA kits (CeditestO CSF E2 Ab ELISA) and SN method. Those results display that pigs after double vaccinations with E2 subunit marker vaccine, either at 2- and 6-week-old or 4- and 8-week-old, can develop strong immune responses and those antibodies can maintain as high ELISA titer with narrow derivation (PI value =103.53-104.86% or SN= 7.57-8.1 log2 ) to marketing. In contrast, pigs with single vaccination at 4-week-old developed moderate immune response compared those with double vaccinations. However, those induced antibodies also persisted to marketing (PI value =88.44%15.58 or average SN = 6.221.2 log2). Moreover, the induction of immune response by E2 subunit marker vaccine was not interfered by maternal antibody, even though 2- week-old piglets with high maternal antibody (PI value =97.97%10.54 , average SN = 7.251.13 log2) were shot with E2 subunit marker vaccine once. To evaluate the efficiency of the E2 subunit marker vaccine in the control of CSF virus persistence, surveillance by pathology, antigen ELISA, RT-PCR and discriminated Erns antibody on sick growers or healthy finishers were regularly monitored. Before the application of E2 subunit vaccine in the trial farm, low frequency of Erns antigen and moderate levels of Erns antibody could be persistently detected in sick growers. However, there was no more evidence of CSF virus infection in the trial farm after E2 subunit marker vaccine applied. Moreover, an experiment of protective efficiency of E2 subunit marker vaccine on vaccinated pigs following with high virulent CSF virus challenge was conducted. The results display that pigs 2 weeks post vaccination (WPV) have developed protective immunity against virulent virus challenge, but still show mild transit clinical signs. There was no clinical signs, leukopenia, virus shedding, viremia, and pathological lesions in those pigs challenged with high virulence CSF virus 3 WPV or boosted with E2 subunit marker vaccine 4 weeks later. Taken those results together, CSF E 2 subunit maker vaccine can efficiently induce high levels of E2 antibody and protect pigs from CSF virus infection that may be helpful in control virus persistent infection in virus contaminated pig farm and promotion of CSF eradication program in Taiwan.
|Appears in Collections:||獸醫病理生物學所|
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